The invention relates to a multisignal combiner for weighting and summing outputs of a two dimensional signal processor so that the output having the best desired signal performance is given the greatest weight.
In the preferred embodiment, the invention is used as a multisignal combiner for weighting the outputs of the two dimensional kernel adaptive interferference suppression system, described in the latter mentioned patent application, according to their performances. This system uses an Adaptive Locally Optimum Detection (ALOD) algorithm which was created especially for interference suppression. This two dimensional suppression system of the prior filed patent application will be referred to hereinafter as the ALOD Processor or Processor. The ALOD algorithm implements kernel estimation to attempt to represent the joint probability density function of two random variables (magnitude and phase-difference) based upon a finite number of data points (signal samples). The algorithm provides an estimate of interference statistics based on such things as atmospheric noise, jamming and other communication signals, so that the received signal samples may be transformed into perceptible communication signals.
The ALOD Processor calculates and outputs two transforms, one based on the amplitude and the other based on the change in phase of received signal samples. These two outputs are then combined with a bleed through path signal from a radio receiver to produce a final output signal which best represents the desired communication signal. Unfortunately, there are signal environments where one or neither of the transform outputs enhance the desired communication signal relative to interference. There are some instances where they may actually degrade the communication signal levels relative to noise levels.
While testing the ALOD Processor I discovered that the performance of each transform output was linked to the value of its corresponding variance. When the variance of the amplitude samples was small, the amplitude transform output provided excellent interference suppression. When it was large, it could actually degrade the communication signal. The same held true for the phase difference transform. When the variance of the phase difference samples was small, the phase difference transform output provided excellent interference suppression. When it was large there could be a degrading of the communication signal. It was this discovery that led to the present invention.